Go to the homebrew channel.
Run the MIOS 7 or 8 (or whatever number) patcher.
Press X on the gamecube controller to make it compatibnle with backup launchers.
Then press A on the gamecube controller to install the program.
If you have Softmii or another app that allows you to launch burned games directly from the disk channel, you should be able to play burned gamecube games similarly.